Purchasing stock from a partnership does not require you to file a business form. The partnership itself files form 1065, with a schedule K-1 for each partners. With a schedule K-1, you'll need TurboTax Deluxe or Premier, depending on the activity flowing through the partnership (most likely Premier for MLPs).
If you own a partnership and need to file the 1065 form, then you're correct to use TurboTax Business.